title: Mechanistic modeling of destratification in cryogenic storage tanks using ultrasonics.
abstract: Stratification is one of the main causes for vaporization of cryogens and increase of tank pressure during cryogenic storage. This leads subsequent problems such as cavitation in cryo-pumps, reduced length of storage time. Hence, it is vital to prevent stratification to improve the cost efficiency of storage systems. If stratified layers exist inside the tank, they have to be removed by suitable methods without venting the vapor. Sonication is one such method capable of keeping fluid layers mixed. In the present work, a mechanistic model for ultrasonic destratification is proposed and validated with destratification experiments done in water. Then, the same model is used to predict the destratification characteristics of cryogenic liquids such as liquid nitrogen (LN₂), liquid hydrogen (LH₂) and liquid ammonia (LNH₃). The destratification parameters are analysed for different frequencies of ultrasound and storage pressures by considering continuous and pulsed modes of ultrasonic operation. From the results, it is determined that use of high frequency ultrasound (low-power/continuous; high-power/pulsing) or low frequency ultrasound (continuous operation with moderate power) can both be effective in removing stratification.
authors.affiliation: Particle Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600 036, India.
authors.forename: T K
authors.initials: TK
authors.lastname: Jagannathan
authors.forename: Srijith
authors.initials: S
authors.lastname: Mohanan
authors.forename: R
authors.initials: R
authors.lastname: Nagarajan
mesh_terms: D000641:Ammonia / Q000737:chemistry* / Q000528:radiation effects; D003198:Computer Simulation; D019220:High-Energy Shock Waves; D006859:Hydrogen / Q000737:chemistry* / Q000528:radiation effects; D008956:Models, Chemical; D009584:Nitrogen / Q000737:chemistry* / Q000528:radiation effects; D011829:Radiation Dosage; D012034:Refrigeration / Q000295:instrumentation / Q000379:methods*; D012212:Rheology / Q000379:methods*; D013010:Sonication / Q000379:methods*
chemical_list: D000641:Ammonia; D006859:Hydrogen; D009584:Nitrogen
keywords: Acoustic cavitation; Acoustic streaming; Cryogenic storage; Thermal stratification; Ultrasonics